It's well known that, angelicin, an angular furocoumarin, could bind to double strand DNA through the UV radiated at 365 nm. The mechanism involved the [2+2] cycloaddition between (3,4) or (4,5)-double bonds of the furocoumarin and the 5,6 double bond of pyrimidine base on the double strand DNA. This photoreaction is directed to two steps reaction. The first step is furocoumarin and DNA formation of a molecular complex. The subsequent irradiation of the complex molecules at UV 365 nm leads to covalent binding of furocoumarins to DNAs. (L. Musajo et al., “Photoreactions at 3655A between pyrimidine bases and skin-photosensitizing furocoumarins, Photochemistry and Photobiology”, Vol. 6, pp711-719, 6 (1967) and G. Rodighiero, et al, “Mechanism of skin-photosensitization by furocoumarins: photoreactivity of various furocoumarins with native DNA and with ribosomal RNA”, Biochim. Biophys. Acta, 217, 40 (1970).
Several derivatives of the angelicin have been synthesized and compared their binding ability to DNA, including 4′-(hydroxymethyl)-4,5′-dimethylangelicin, 4′-(methoxymethyl)-4,5′-dimethylangelicin, and the hydrochloride of 4′-(aminomethyl)-4,5′-diemthylangelicin. The more water solubility of furocoumarin showed more binding ability to the DNA. (F. Dall'Acqua, et. al., “New monofunctional reagents for DNA as possible agents for the photochemotoerapy of psoriasis: Derivatives of 4,5′-dimethylangelcin”, J. Med. Chem. 1981, 24,178-184).
Furocoumarins, which are linked to biotin with the suitable spacer molecules, have been shown to be very suitable for the photobiotinylation of nucleic acids. After hybridization to a gene probe with a complementary nucleic acid sequence, and a separation step, detection takes place, for example by addition of a complex of antibiotin antibody or avidin or streptavidin with alkaline phosphatase. For the detection, a color reaction, which is elicited by alkaline phosphatase, is carried out in an additional step (J. J. Leary, D. J. Brigati, D. C. Ward, Proc. Natl. Acad. Sci. USA 80, 4045-4049 (1983)).
In the description of U.S. Pat. No. 5,616,731, one disadvantage of the detection system using biotin is the wide distribution of biotin in biological systems. This disadvantage is avoided by using, for example, digoxigenin instead of biotin. Surprisingly, no denaturation of the nucleic acids has been observed in photoreactions with digoxigenin reagents, which are linked to furocoumarins by means of a suitable spacer.
Nicolaus Bahr et al., “A nitroxyl synthase catalytic antibody,” J. Am. Chem. Soc. 1996, 118, 3550-3555 described the use of an antibody raised against acridinium hapten to analyze the retro Diels-Alder reaction of the anthracene-HNO cycloadduct to release anthracene and nitroxyl (HNO).
Maciej Adamczyk et al., “Neopentyl 3-Triflyloxypropanesulfonate” J. Am. Chem. Soc. 1998, 63, 5636-5639 described a reactive sulfopropylation reagent for the preparation of chemiluminescent labels.